Waiting to have kids until later in life? You’re doing some good for the planet, too

Throughout the industrialized world, moms are getting older. The average age of first-time moms in the US has been steadily on the rise in the 21st century, reaching 26.3 in 2014—more than a year older than in 2000. The average age of a first-time mom in Canada is 28.5; the same is true in Finland. The average age is 29.2 in Germany and 30.3 in Japan. And women are also having fewer children: Most industrialized nations are currently hovering at replacement rate (2.1 children per woman, on average), and many, especially in Europe, are at sub-replacement levels.

What are we to make of this trend? It’s true that women can have a harder time getting pregnant once they’re in their mid-30s, as well as face certain health risks. But there are also advantages to having kids later in life. Recent studies have found that older moms resort to physical and verbal abuse less often and that their children have fewer behavioral issues. Some studies have even found that children of older moms tend to be taller and score higher on intelligence tests. Older moms live longer on average. And it turns out that having children later in life is also good for the environment.

The number of humans on the planet is directly connected to the amount of carbon we’re releasing into the atmosphere. Slow down population growth, and you’ve got fewer carbon emitters to contend with. That’s where waiting longer to have kids comes in.

Older moms tend to have fewer children than their younger counterparts, in part because their reproductive window is smaller. ““One possible consequence is that as you delay the birth of the first child, the possibility of having three or more children becomes problematic,” Brady E. Hamilton, a statistician with the National Center for Health Statistics, told The New York Times. “So the longer you postpone, the more potential you have for smaller families and smaller population growth.”

Even if an older mother has the same number of kids that she would have had at a younger age, she does the environment a favor by spacing out those births—so that fewer people are on the planet at the same time.“When you delay childbearing, when you have children later, you stretch out the wave of oncoming children and so there are fewer children in any given year than there would have otherwise been,” says Robert Engelman, a former science reporter and current senior fellow at the Worldwatch Institute, an environmental research organization focused on global sustainability. This so-called “tempo effect” is temporary, but it helps mute the overall impact that humans have on the environment.

Engelman acknowledges that there’s a tricky aspect to calling for smaller families, in that it can be read as an attempt to control or influence women’s reproductive choices. But he says that the proper environmental goal is simply to expand access to family planning so that women can have as many healthy pregnancies as they want—when they want them. “I’ve talked to maybe hundreds of women in developing countries and the United States about this topic and so few tell me that they want to have 10 children that I’m not worried about it,” he says. “The vast majority of them say, ‘I want to have two or fewer, maybe three.’”

In much of the world, the possibility of choosing to postpone motherhood is out of reach, since women lack access to reproductive health care. “Right now in rural Nigeria, in rural Mali, if you want only four children there is no way to do that,” says John Bongaarts, vice president and distinguished scholar at the nonprofit Population Council. “You’re going to end up with seven or eight … What these women need is access to contraceptives. Women very badly want to control their fertility.”

Despite lower overall fertility rates, Bongaarts notes that reproductive choice is still an issue in the US and other industrialized nations. “I wouldn’t dismiss the effects of access to contraception in rich countries,” he says. “We still have unwanted pregnancies.” The Guttmacher Institute, which Engleman cited as the gold standard in reproductive health research, estimates that about 45% of all pregnancies in the US are unintended. Given unfettered, affordable access to birth control, women in the US would likely have even fewer children at a later age.

And rich countries like the US are the biggest carbon consumers by far. “Most of the carbon is produced in countries where fertility is low,” says Bongaarts. Making it possible for women to have fewer children at a later age around the world—in rich and developing countries alike—is a good way to invest in the future of the global environment.

“The fewer children you have and the longer you wait to have them, the better it will be for the future of the planet; the less carbon emissions there are going to be,” says Engelman. “It’s an issue of scale and momentum.”

So if the term “advanced maternal age”—now preferred to the truly horrifying “geriatric pregnancy”—makes you cringe, take heart. There are a lot of good things about being an older mom, including the fact that you can help your tall, smart, well-adjusted children grow up to be environmentally conscious types too. Maybe they’ll walk or bike everywhere instead of driving. They’ll have long legs, after all.